In the rich text editor:
@garlitbread
In a comment:
[garlitbread](https://chowlings.com/user/garlitbread)
For Names and Avatars:
In the rich text editor:
%garlitbread
In a comment:
[![garlitbread's Avatar](https://chowlings.com/images/avatars/default.jpg)](https://chowlings.com/user/garlitbread) [garlitbread](https://chowlings.com/user/garlitbread)